The present disclosure generally relates to the field of batteries and battery modules. More specifically, the present disclosure relates to methods to obtain improved fuel economy and battery life in systems employing battery systems with battery modules having different chemistries.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term “xEV” is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. For example, xEVs include electric vehicles (EVs) that utilize electric power for all motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs), also considered xEVs, combine an internal combustion engine propulsion system and a battery-powered electric propulsion system. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Further, a micro-hybrid electric vehicle (mHEV) also uses a “Stop-Start” system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered as an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives or contributes to drive the wheels. PEVs are a subcategory of EVs that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.
xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of EVs or PEVs.
In addition to use in vehicles (e.g., vehicles, boats, trucks, motorcycles, and airplanes), advances in battery technology and rechargeable batteries are more frequently being used in what may be referred to as stationary battery applications. Applications for stationary batteries, which are often used in backup or supplemental power generation, are becoming more widespread with improvements in rechargeable aspects of batteries and with the lowering of prices for such technology. For example, stationary batteries may be utilized for industrial and/or household applications. Such applications may include DC power plants, substations, back-up power generators, transmission distribution, solar power collection, and grid supply.
Managing energy storage systems to achieve optimal performance can be a challenge especially when service conditions vary and components age. As technology continues to evolve, there is a need to provide improved management of the state and capacity for battery modules of such vehicles, stationary battery applications or systems, and other battery systems to improve energy utilization and battery lifetime. For example, the electric power used by xEVs may be provided by battery systems that include cells using batteries with different chemistries. The different battery chemistries may have different electrical properties such as charging capacity and capacities and which may provide complementary characteristics to improve the performance of the system. For example, a battery system may have a lithium-ion battery, which allows efficient recharging, and a lead-acid battery, which has a better discharge performance (e.g., for cold cranking an engine).